1. Technical Field
Charging an auxiliary battery in a plug-in electric vehicle using a power supply external to the vehicle.
2. Background Art
A hybrid electric vehicle (HEV) generally includes a high-voltage storage battery, a secondary battery, a combustion engine, and an electric motor. The high-voltage storage battery has a state of charge (SOC). However, the SOC of the battery decreases when the high-voltage storage battery provides electric power for the vehicle. For example, the SOC of the high-voltage storage battery decreases when providing electric power to the electric motor to drive traction wheels on the vehicle. In such an example, the electric power stored in the high-voltage storage battery decreases and the electric-only driving range of the HEV is reduced.
The secondary or auxiliary battery operates at a lower voltage than the high-voltage storage battery, such as 12-volts. The secondary battery can provide electric power to drive various low-voltage loads in the HEV. However, the amount of electric charge in the secondary battery decreases when driving various loads in the HEV. Consequently, the secondary battery may need to be recharged by transferring electric power from energy stored on the vehicle to the secondary battery. Such stored energy may be in the form of electrical energy stored in the high-voltage storage battery or from stored fuel that is converted by an engine-driven generator to electrical energy and transferred to the secondary battery. However, using stored onboard energy to recharge the secondary battery can reduce the driving range and overall efficiency of the HEV.